The present invention is directed to cooling assemblies and other apparatus used for removing heat from electronic devices. More particularly, the present invention is directed to an apparatus for cooling an electronic module through the selective utilization of thermoelectric cooling elements. Even more particularly, this invention is directed to a thermal spreading plate having at least one thermoelectric cooling element associated with only a portion thereof. The at least one thermoelectric cooling element is positioned to align to an area of higher heat flux on a surface of the heat generating element to be cooled.
As is well known, as the circuit density of electronic chip devices increases, there is a correspondingly increasing demand for the removal of heat generated by these devices. The increased heat demand arises both because the circuit devices are packed more closely together and because the circuits themselves are operated at increasingly higher clock frequencies. Nonetheless, it is also known that runaway thermal conditions and excessive heat generated by chips is a leading cause for failure of chip devices. Furthermore, it is anticipated that the demand for heat removal from these devices will increase indefinitely. Accordingly, it is seen that there is a large and significant need to provide useful cooling mechanisms for electronic circuit devices.
The use of large thermoelectric cooling elements is known. These elements operate electronically to produce a cooling effect. By passing a direct current through the legs of a thermoelectric device, a temperature difference is produced across the device which may be contrary to that which would be expected from Fourier""s Law.
At one junction of the thermoelectric element both holes and electrons move away, toward the other junction, as a consequence of the current flow through the junction. Holes move through the p-type material and electrons through the n-type material. To compensate for this loss of charge carriers, additional electrons are raised from the valence band to the conduction band to create new pairs of electrons and holes. Since energy is required to do this, heat is absorbed at this junction. Conversely, as an electron drops into a hole at the other junction, its surplus energy is released in the form of heat. This transfer of thermal energy from the cold junction to the hot junction is known as the Peltier effect.
Use of the Peltier effect permits the surfaces attached to a heat source to be maintained at a temperature below that of a surface attached to a heat sink. What these thermoelectric modules provide is the ability to operate the cold side below the ambient temperature of the cooling medium (air or water). When direct current is passed through these thermoelectric modules a temperature difference is produced with the result that one side is relatively cooler than the other side. These thermoelectric modules are therefore seen to possess a hot side and a cold side, and provide a mechanism for facilitating the transfer of thermal energy from the cold side of the thermoelectric module to the hot side of the module.
Conventional configurations of large thermoelectric assemblies are nonetheless seen herein to be unnecessarily limiting in terms of their application to the transfer of thermal energy. Thus, while the use of thermoelectric devices is seen to provide a means for the solid state cooling of adjacent electrical devices, their efficiency has been less than optimal.
In addition, complementary metal oxide semiconductor (CMOS) semiconductor processing has progressed to the point where multiple logic units (such as processors) and their associated control and support circuits (e.g., memory) are being placed on a single integrated circuit chip. From a thermal viewpoint, this results in a chip with a highly non-uniform heat flux distribution. A relatively high heat flux is generated in the processor core region(s) and a relatively low heat flux is produced by the control/support regions. In fact, the core region heat flux can be as much as fifteen times greater than that of the other regions. Thermal paste conduction cooling schemes are not well suited to handle such disparate fluxes. They result in an equally disparate circuit temperature distribution, and more importantly, a much higher absolute junction temperature within the high heat flux regions.
To summarize the present invention, therefore, provided herein in one aspect is thermal dissipation subassembly for facilitating cooling of an electronic device, such as a module. The thermal dissipation subassembly includes a thermal spreader which is configured to thermally couple to a surface of a heat generating component. The heat generating component has a non-uniform thermal distribution across the surface between at least one first region of the surface and at least one second region of the surface. The at least one first region has a higher heat flux than the at least one second region. The thermal dissipation subassembly further includes at least one thermoelectric device aligned to at least a portion of the at least one first region of the surface having the higher heat flux, wherein the at least one thermoelectric device facilitates dissipation of the higher heat flux.
In another aspect, the present invention comprises an electronic device including a heat generating component having a non-uniform thermal distribution across a surface thereof between at least one first region of the surface and at least one second region of the surface, with the at least one first region having a higher heat flux than the at least one second region. The electronic device further includes a thermal dissipation subassembly having a thermal spreader and at least one thermoelectric device. The thermal spreader thermally couples to the surface of the heat generating component, and the at least one thermoelectric device aligns to at least a portion of the at least one first region having the higher heat flux, wherein the at least one thermoelectric device facilitates dissipation of the higher heat flux.
In a further aspect, a method of fabricating a thermal dissipation subassembly for an electronic device is presented. The method includes: providing a thermal spreader configured to thermally couple to a surface of a heat generating component of the electronic device, the heat generating component having a non-uniform thermal distribution across the surface between at least one first region of the surface and at least one second region of the surface, wherein the at least one first region has a higher heat flux than the at least one second region; and disposing at least one thermoelectric device over the surface having the thermal spreader coupled thereto and aligned to at least a portion of the first region having the higher heat flux, wherein the at least one thermoelectric device facilitates dissipation of the higher heat flux.
To restate, provided herein is a thermoelectric-enhanced heat spreader subassembly useful in cooling a heat generating component such an integrated circuit chip. One or more thermoelectric cooling units, which are embedded within or reside adjacent to a thermal spreader plate, are aligned to selected regions of higher heat flux of the heat generating component. By selectively using thermoelectric cooling units only where needed, enhanced thermal performance is obtained while limiting costs associated with that performance. The thermoelectric cooling units are unidirectional heat transfer devices, while the thermal spreader plate spreads heat radially to regions of lower power. Heat can ultimately be dissipated through an electronic module cap or heat sink disposed adjacent to the thermal spreader and thermoelectric unit subassembly. A subassembly in accordance with the present invention allows handling of high heat flux zones on a component, such as an integrated circuit component, while cooling the entire chip to acceptable temperatures thereby establishing a more uniform temperature distribution on the component. This advantageously facilitates integrated circuit design and operation.
Additional features and advantages are realized through the techniques of the present invention. Other embodiments and aspects of the invention are described in detail herein and are considered part of the claimed invention.